LESSER WHITETHROAT 
namely, that supplied by fortuitous variation and selection ; 
and in order that this may have been effecttal, it must be 
taken for granted that any one given species has suffered 
constant persecution at the hands of some natural enemy or 
enemies. What the enemies are, which have been so misled 
by these proceedings that advantage has accrued to the 
individuals thus practising them, I find it difficult to imagine. 
It surely cannot be thought that the human element has been 
a factor; for consider, in the case of a little Warbler, how 
immense a period of time would be necessary, and how 
constant the persecution must have been before selection 
could have completed its task, and the variation have become 
fixed, and finally established as an instinct uniform throughout 
the species. Nor, after carefully surveying the life-history of 
the species in which the habit is prevalent, is it more satis- 
factory to regard carnivorous quadrupeds as the principal 
factor; yet it is to them that the selectionist must look. At 
the same time we must bear in mind the past history of the 
species, the enormous periods of time, and the possibility 
of the habit having been formed at some very early date when 
the conditions of existence were more strenuous, and enemies 
more numerous, but even if we grant all this imperfection 
of our knowledge, it is but a frail foundation upon which to 
raise a theory. 
Let us look at the facts more closely. I have described 
a number of cases in which—and this no doubt is true of every 
case of the same kind—similar stimulating circumstances 
produce similar results, and in whatever way we may regard 
any one particular case, this much must be granted, that no 
distinction is scientifically possible between the behaviour of 
the Avocet on the one hand, and that of the Lesser White- 
throat on the other; we cannot, that is to say, point to the 
apparently injured leg or wing of the Avocet, and, because it 
thus approaches more nearly our conception of a wounded bird, 
proceed to argue that therefore its behaviour is different in 
kind, and capable of a different explanation from that of the 
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